Transponder detection system and method
First Claim
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1. A transponder detection system for detecting the presence of a transponder-equipped vehicle at a detection zone, a transponder transmitting RF signals, comprising:
- an antenna array comprising a plurality of antenna elements defining an array boresight, said boresight intersecting said detection zone;
receiver means coupled to said antenna array and responsive to transponder transmissions for providing an array sum signal that represents a sum of signal contributions from each antenna element of said antenna array, and an array difference signal that represents a difference of signal contributions from said each antenna element of said antenna array; and
processing means responsive to said array sum and difference signals to determine whether the transponder is located within the detection zone, said processing means comprising means responsive to said array sum signal to determine whether a valid transponder signal has been received by the system, the means responsive to said difference signal to determine whether said transponder is located within the detection zone.
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Abstract
A transponder detection system for detecting the presence at a detection area of a vehicle on which the transponder is mounted. Two antenna arrays are located on opposite sides of the detection area, and have their boresights directed to the detection area. For each array, a sum and difference signal of signals received from the transponder are measured. The sum channel signal is used to establish whether a transmission has occurred, and the difference channel signal is used to isolate any transponder that is at the detection area.
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Citations
21 Claims
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1. A transponder detection system for detecting the presence of a transponder-equipped vehicle at a detection zone, a transponder transmitting RF signals, comprising:
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an antenna array comprising a plurality of antenna elements defining an array boresight, said boresight intersecting said detection zone; receiver means coupled to said antenna array and responsive to transponder transmissions for providing an array sum signal that represents a sum of signal contributions from each antenna element of said antenna array, and an array difference signal that represents a difference of signal contributions from said each antenna element of said antenna array; and processing means responsive to said array sum and difference signals to determine whether the transponder is located within the detection zone, said processing means comprising means responsive to said array sum signal to determine whether a valid transponder signal has been received by the system, the means responsive to said difference signal to determine whether said transponder is located within the detection zone. - View Dependent Claims (2, 3, 4)
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5. A transponder detection system for detecting the presence of a transponder-equipped vehicle at a detection zone, a transponder transmitting RF signals, comprising:
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first and second antenna arrays, each array comprising a plurality of antenna elements defining an array boresight, said antenna arrays disposed at spaced locations relative to the detection zone, each array boresight directed at said detection zone; receiver means responsive to transponder transmissions for providing an array sum signal that represents a sum of signal contributions from each antenna element of said antenna arrays, and an array difference signal that represents a difference of signal contributions from each antenna element of said antenna arrays; and processing means responsive to said respective array sum and difference signals to determine whether the transponder is located within the detection zone, said processing means comprising means responsive to said sum signal to determine whether a valid transponder signal has been received by the system, and means responsive to said difference signal to determine whether said transponder is located within the detection zone. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
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14. A barrier-based toll collection system for determining vehicle tolls for access to a toll roadway, comprising:
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a toll collection barrier area defining a vehicle detection zone; a vehicle detector for detecting the presence of a vehicle at said detection zone; a toll collection apparatus for collecting tolls assessed to vehicles entering said detection zone which are not equipped with a transponder; a transponder detection system responsive to said vehicle detector for detecting the presence of a transponder-equipped vehicle at said detection zone, the transponder transmitting RF signals, comprising; first and second antenna arrays, each array comprising a plurality of antenna elements defining an array boresight, said antenna arrays disposed at spaced locations relative to the detection zone, each array boresight directed at said detection zone; receiver means responsive to transponder transmissions received from said vehicle for providing an array sum signal that represents a sum of a signal contributions from each antenna element of said antenna arrays, and an array difference signal that represents a difference of signal contributions from each antenna element of said antenna arrays; and processing means responsive to said respective array sum and difference signals to determine whether the transponder-equipped vehicle is located within the detection zone, said processing means comprising means responsive to said sum signal to determine whether a valid transponder signal has been received by the system, and means responsive to said difference signal to determine whether said transponder-equipped vehicle is located within the detection zone;
means responsive to said detection system processordetermination that said detected vehicle at said detection zone is transponder-equipped for suppressing said toll collection apparatus and for electronically issuing a toll charge to said transponder-equipped vehicle. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification